Tuesday, November 21, 2017

Buckthorn eradication: a 20-year story

This post is based on 20-years work restoring oak savannas
and tallgrass prairie remnants at PVC. During that period, we were able to
obtain a lot of experience on the eradication of invasive woody plants, of
which buckthorn was the most difficult. See the table at the end for an index to my blog posts that dealt with buckthorn.

Common buckthorn (Rhamnus
cathartica) is the #1 invasive shrub on the IPAW list. When we started serious restoration work at Pleasant Valley
Conservancy in 1997, it was present in very dense patches throughout most of
the savanna areas. Later I discovered that buckthorn is a calciphile, and was growing
mainly in high-calcium high-pH soils derived from or influenced by dolomitic
rocks. In many of the calcium-rich oak savanna areas, the understory was almost a buckthorn
monoculture.

During our major restoration work, buckthorn was removed at
the same time as all the other invasive woody plants. Buckthorn removal mainly
involved cutting the buckthorn thickets with a brush cutter or chain saw, and
treating all the cut stems with herbicide (generally Garlon 3A at 15-20%). Buckthorn
was not the only “bad” plant in our degraded oak savannas, but in the
calcium-rich areas it was the principal one. The mature open-grown savanna oaks
were also being crowded by invasive trees such as walnut, elm, cherry. There
were even some “bad” oaks, such as the more rapid-growing oaks of the black oak
group, and these were removed also.

According to my notes, all of the large patches of buckthorn
were removed during the major clearing that took place in 1998 through 2004.

Once the savanna areas were cleared, fire was introduced as a
principal tool. Although the use of fire was important, it only top-kills woody
plants. The underground rootstock remains alive, and quickly resprouts. In
fact, there is a strong “legacy” of woody plants in any formerly wooded area.
If a cleared area is abandoned, it will quickly become overgrown again.

Although this “legacy” is important for most woody species,
it is especially severe with buckthorn. It took me some years to discover that with
buckthorn there are three legacies:

1.Buckthorn
produces a toxic chemical called emodin which inhibits the growth of other
plants and prevents “good” plants from becoming established. It creates what we
have called a “buckthorn desert”. It generally takes about three years for the
toxic chemical to dissipate.

2.An
extensive seed bank from the large number of berries produced. (Although only
the female buckthorn plants produce berries, the ratio of female to male plants
can be as high as 6:1.) The seed bank only lasts a few years.

3.An
extensive rootstock (sometimes called a caudex) from which new shoots can
arise. It took me some years to realize that the rootstock of the buckthorn can
remain dormant from many years.

In the earlier years of our restoration work I did not realize the seriousness of the buckthorn problem. (I hardly mentioned it in the new management plan I wrote in June 2005.) It was not until 2006-2007 when we did our major “all-out” push to clear brambles and other woody shrubs that had arisen since the initial restoration work, that I became aware that we also had a buckthorn problem.

By this time I had started my first Blog (Tom’s Journal),
and buckthorn was a major topic. The table at the end of this document gives
links to the various Blog posts.

There is a lot of internet material on buckthorn, mostly
focusing on getting rid of it. Most of this work is based on short-term
studies, or on anecdotal evidence. Buckthorn has a complicated ecology, which
enters into a discussion of control methods.

Through the 20-year period that I have been following
buckthorn I determined that buckthorn rootstock can be long-lived, and remain
dormant for many years. Thus, an area that once had had a large buckthorn
infestation can have numerous invisible and dormant rootstocks.

In order to get some quantitative data, in 2010 I chose a
site of about 100 X 100 feet where buckthorn had been removed around 2000 but
kept coming back. I canvassed the site carefully and sprayed each buckthorn
shoot with Garlon 3A (foliar at 4% aqueous). Most of the plants had only single
shoots, but some had more than one. I sprayed all the shoots I could find at
each survey.

In the three early years, when there were lots of shoots, I
returned over and over again at 2-3 week intervals, and sprayed all the “new”
buckthorn shoots that had arisen. At the end of each season, I made sure that
there were no live buckthorn shoots left.

The table shows the results. My conclusion was that in this
small, buckthorn-rich area, there were many dormant rootstocks, but not all of
them left dormancy the same year.

Year

Buckthorn shoots
sprayed

Year total

2010

not recorded

>300

2011

12 + 30 + 71 + 35 + 27

175

2012

17 +18 + 55 + 5 + 44 + 20 + 82

241

2013

6 + 7 + 8

21

2014

0

0

Buckthorn resprouts, waiting to be sprayed! These could be either fromfire-killed plants or from dormant rootstock

I should emphasize that the original removal of buckthorn
was in either 1999 or 2000. Unanswered is what stimulates these dormant
rootstocks to start growing after many years?

My conclusion is that buckthorn might be eradicated from a
site, but it might take many years.

Note that the area I studied had been heavily “infected” by
buckthorn, and that there was plenty of time for the plants to make extensive
underground rootstocks. Sites recently colonized by buckthorn might be
eradicated much easier. However, I suspect that most sites in southern
Wisconsin that are full of old-growth buckthorn would be similar to my site,
especially if they had dolomitic soils.

A single buckthorn plant still green after the native vegetation has senesced.Can be sprayed without causing any peripheral damage,with either glyphosate or triclopyr

Today Pleasant Valley
Conservancy is virtually free of buckthorn! This is because we have worked
very hard to kill the plant when we see it. Every year, we canvass all sites
where buckthorn has been a problem.

We are especially helped by the fact that all of the savanna
areas, where buckthorn had been the biggest problem, are burned each year. Fire
keeps buckthorn at a juvenile status, and prevents any extensive spread by
underground roots or rhizomes. Fire makes it possible for us to spray buckthorn
shoots when they are still small (foliar spraying is done in the spring).

Any buckthorn plants not killed in the spring can be killed when
they are found in summer, autumn, or winter by basal bark treatment. The dark
shiny leaves of buckthorn plants make them easy to spot, especially in the fall
of the year when native vegetation has senesced.

Single buckthorn stem that had been basal-barked with 20% Garlon 4 in oil. The leaves are curledand dying.

Blog posts through the years on buckthorn. The ones before 2008 are no longer available

Thursday, November 9, 2017

Can Brambles Be Eradicated From Prairies and Savannas? A Long Story

Brambles (genus Rubus) may be native but they are
generally undesirable in a prairie or savanna. This post is based on over 20
years of restoration work at Pleasant Valley Conservancy.

The story starts when Kathie
and I first started clearing invasive brush and trees from prairie and savanna
remnants at PVC in 1997. There was lots of bad stuff: shrubs such as buckthorn,
honeysuckle, and prickly ash and trees such as elm, cedar, red pine (planted),
box elder. If there were brambles, we did not notice them. Probably they were
shade-suppressed.

But once the site was opened
up, brambles started to flourish. Originally they were just small patches, which
in our ignorance we ignored. In 1999 some of these bramble patches were large
enough that we got rid of them. There may have been some larger patches, but in
a property as large as Pleasant Valley Conservancy, it was easy to overlook
them.

What was the source of these brambles? Both buried
root stock and buried seeds are likely. I doubt the root stock is long lived,
but Rubus seeds are notoriously
long-lived. (A U.S. Forest Service studyin New England found viable Rubus seeds that had been buried for 95
years.)

The Ecology of Brambles

Brambles are members of the
genus Rubus. They have perennial
roots systems but biennial tops. The roots continue to spread but new canes are
formed each year. The first year cane just grows vegetatively and in the second
year flowers and forms fruits. After fruit formation it dies. Thus, a bramble
patch is a mixture of first year and second year canes, as well as dead canes
which senesce.

We have three species of Rubus at PVC: blackberries, black
raspberries, red raspberries. All are bad, and we do not distinguish between
them, although red raspberries presents a special challenge.

The First Survey

It was 2005 before brambles
started to be so obvious that we could not ignore them. That year I made a
survey, marking each patch with a numbered stake. There were 17 patches, all in
open savannas. My notes in the table here give some idea of how large these bramble
patches were.

Data from June 5-6 2005

Stake #

Unit #

Location

Notes

1

12A

~75 ft below the upper road (below Toby’s); large patch in
flower

White Oak Savanna

2

12A

~75 ft farther down the hill from #1; edge of Unit 12E;
large patch in flower

White Oak Savanna

3

12A

Smaller patch but taller stems west of #1

White Oak Savanna

4

12C

Large patch among two large dead oaks; also outliers east
and downhill

White Oak Savanna

5

12C

About 75 ft east of trail down; along a drainage; follow
the drainage up and down

White Oak Savanna

6

11A

Edge of open area and edge of ridge; shorter plants but
lots; forming berries

Bur Oak Savanna

7

11A

Near road; low but lots forming berries

Bur Oak Savanna

8

11A

50 fit West of #7 near fallen oak

Bur Oak Savanna

9

13B

Lots of 1st year plants mixed in with Geraniuum
etc. Can cut it all. Whole top of knoll, also

Woods near east property boundary

10

17

N of Toby’s in former aspen zone; scattered but large
patch; 1st year plants

Between Toby’s NE corner and woods

11

11B

Above Paul Ihm’s wood pile

Bur Oak Savanna

12

11A

SE corner of saddle; large patch with little good; mow up
hill and to the east also

Bur Oak Savanna

13

23

Large patch of low brambles; uphill to the west from the
saddle; do the whole patch

East-facing hill above Hickory Ravine

14

7

Very large patch uphill from Hickory Ravine; mow down hill
and to the east

15

6

Top of hill near fire break; 75 ft west of side road;
large patch of low brambles; mow down the hill and into the gully

16

10

Across the fire break from stake #15; big patch mixed in
with brush; cut it all and then treat the brush

Should have a second person with you for treating the cut
stumps

17

5C/5B

West of Unit 4 along and below the fire break on both
sides of the gully; huge area

This is a two-three person job!

Getting Serious

At that time the only
information I could find about how to eradicate brambles was: Mowing several times a year will reduce
their vigor.

Reducing vigor did not sound
like a promising method for eradication.

By the late fall of 2005
Kathie and I had decided that our goal should be to get rid of all brambles, as
well as other invasive brush that had sprung up in our restored areas. After
all, we had spent a lot of effort opening up these prairies and savanna. If we
did not get rid of all these new invaders, we could be back where we started.
An awful thought!

We experimented with several
different methods of herbicide application: foliar spraying the bramble patches
(low herbicide concentration); basal bark (high concentration, in oil); cut and
treat the cut stems (high concentration, either aqueous of in oil). We rejected
foliar spraying of the large patches because of the possible peripheral herbicide
damage. We tried basal bark, but application from a backpack sprayer was also “wasterful”
of herbicide, and because of the high concentration, there were bare zones
around the treated patches. We also tried a sponge method for basal bark, but
the thorns on the brambles tore the sponges to shreds.

Cut-and-treat method

We chose the “cut-and-treat”
method because only small amounts of herbicide would be used, and it could be
applied carefully by a spray bottle. Because of the extent of the infestations,
this was usually a four- to five-person job. One person operated the Stihl
brush cutter and the others followed along with spray bottles containing 50% glyphosate. Since we were working primarily in
the winter, when it was below freezing we diluted the glyphosate with
windshield washer fluid. Where there was a lot of buckthorn, we used Garlon 4
in oil, which presented no freezing problem in the winter. The “treaters”
fanned out behind the brush cutter and treated each cut stem.

A great advantage of this
method is that it could be done any time of year, and especially at times when
weed work, plant surveys, seed collecting, etc. could not be done. We worked
with a combination of hired employees and volunteers.

I ran some preliminary
versions of this method in late November 2005. We then set up a major effort on
the White Oak Savanna starting in early January 2006. Todd Shumate from Michler
& Brown ran the brush cutter and three or four “treaters” followed behind.
Todd cut every woody shrub in the savanna. Brambles constituted at least half of
the brush, but honeysuckle and prickly ash were substantial.

The brush cutter was equipped
with a saw blade. Todd ran the brush cutter until he ran out of gas (about 45
minutes per tank). He then sharpened the saw blade with a special Stihl file.
This kept the cut stems clean and flat so they could be treated properly. Cut
stems that were dead were not treated. (Living cut stems are green even in the
winter.)

The First Major Effort

The table gives an example of
this work for a five-acre white oak savanna. Finishing the whole unit took 9
days, working about 40 person hours per acre. Fortunately, January of 2006 was
surprisingly mild and snow-free. Often we were in shirt sleeves at noon.

Table shows brush cutting work on Unit 12A (the White Oak Savanna). Total area 5.3 acres

2-Feb-06

31-Jan-06

26-Jan-06

24-Jan-06

19-Jan-06

17-Jan-06

12-Jan-06

5-Jan-06

3-Jan-06

Totals

Todd

5.5

5.25

7

6.75

6.75

6.75

5.5

6.75

50.25

Susan

5.5

5.75

5.25

5.5

5.75

27.75

Elke

5.5

6

5.75

17.25

Tom

5.5

4.9

6

5.5

5.75

5.25

5.5

4

2

44.4

Kathie

5.5

4.9

6

5.5

5.75

5.25

5.5

5.75

2

46.15

Brian

2.25

4.25

2

8.5

Final total

194.3

Averages>>

36.7

hrs/acre

If assume $25/hr, acreage cost is

$917.50

Roughly $1000/acre

Extending the Effort (2006-2007)

Once the White Oak Savanna
work was completed, we extended the work to the rest of the areas where brush
and brambles were rampant. The table shows the 2006-2007 work (81 work days; 30
days in 2006 and 51 days in 2007.)

In 2007 I established winter
intern positions, and we had 3 (or 4) UW-Madison students working two days a
week starting in January and continuing until mid May.

Date

Unit

Notes

7
Feb 2006

18

Lots
of honeysuckle; brambles; prickly ash; walnut resprouts

9
Feb 2006

18

Lots
of honeysuckle; brambles; prickly ash; walnut resprouts

14
February 2006

18

Lots
of honeysuckle; brambles; prickly ash; walnut resprouts

21
Feb 2006

6

Mostly
honeys; small buckth; few brmbles; some dogwood

23
Feb 2006

2
below Diag Trail

Lots
honeys few buckth; fee brmbles

28
Feb 2006

12B

Mostly
brambles

2
Mar 2006

12B

7
Mar 2006

3
(around big bur oak)

Mostly
brambles

7
Mar 2006

19C

Buckth
mostly

10
Mar 2006

6/23

Lots
little buckth

11
Mar 2006

6/23

14
Mar 2006

11

Big
bramble; buckth; prickly ash

21
Mar 2006

11

23
Mar 2006

10

Lots
tiny buckth; brambles

28
Mar 2006

6
(east)

Honeys;
brambles; s umac

30
Mar 2006

19

17
Nov 2006

7

Lower
part and adjacent to 18; shrubs/brambles small honeys; cut & treat glypho

Afer
lunch, 5A too sloppy, moved to 6 lower east around rocks, lots of honeys but
small

12
Mar 2007

5A

13
Mar 2007

5A

Above
Unit 1 and along Ridge Trail; FINISH WHOLE SOUTH SLOPE!!

13
Mar 2007

Quarry

After
lunch

14
Mar 2007

2/19

Finish
Unit 2; start Unit 19

15
Mar 2007

6

along
dolomite shelf

15
Mar 2007

19

20
Mar 2007

19D/E

22
March2007

19C/D

28
Mar 2007

20C/19D

Finish
20C

4
Apr 2007

19C

5
Apr 2007

19C

Fire and Brambles: Spraying Resprouts

Brambles are fairly fire
sensitive and are killed by a controlled burn.

Fire moving through a bramble patch in a savanna. All bramble stems are killed.

Starting in 2008 we added
another method of bramble control: foliar
spraying of resprouts after the bramble canes had been killed by early
spring burns. The details of this method are covered in several Tom’s Blog
posts in 2008, 2009, and 2010.

Although this method is very effective,
it is limited to May or early June, when the resprouts are small enough to
spray without too much peripheral damage. To set up the spraying routine, I
created another bramble database. By then I had learned how to use ArcGIS. On 14 and 16 April 2009 I walked
the whole south side of PVC, recording the coordinates of each patch

After a burn, bramble patches
are fairly easy to spot, as the following photo shows.

Far
E end by fire break; narrow patch along break; also some East of the fire
break

50

43.10448431

-89.80189255

Unit
21

Black
raspberry

4/18/2009

5

Near
top, W of Ridge Prairie; large; good area to plant

51

43.10472043

-89.80143623

Unit
21

Blackberry

4/18/2009

2

Moderate

52

43.10612004

-89.80752091

Unit
6

Black
raspberry

3/19/2009

2

Top
of gully near S fire break; moderate

53

43.10624929

-89.80765586

Unit
6

Black
raspberry

3/19/2009

5

Up
from gully near bur oak grove; large loose clone

54

43.10630059

-89.80788318

Unit
6

Black
raspberry

3/19/2009

2

Nearer
gully than BR53, mixed in with sumac

By the beginning of 2010 we
had fairly good control of brambles except for red raspberry, which forms really
dense patches of brambles with stems growing very close together. The cut-and
-treat method is not recommended because the cut stems are so close together
and it is difficult to keep track of which ones had been treated. Fortunately,
most of the areas where we were cutting and treating did not have red
raspberries.

After almost ten years
working on bramble control, I found that the best way to control red raspberry is to spray (with 3.5% aqueous Garlon 3A) all
the resprouts that arise after burns. However, not all shoots come up at the
same time, so it is necessary to spray again two weeks after the first time,
and again after another two weeks. Monitoring again in mid-summer for any “escapes”,
and again the next year is also advisable.

The importance of annual burns

One of the most important reasons
why annual burns should be done in oak savannas is because of brambles. Putting
savannas on a three-year burn cycle, such as is often done for prairies, is
exceedingly ill advised. Savannas almost always have a “legacy” of woody
invasives, of which brambles are one of the most important. Giving woody
vegetation the chance to grow unimpeded for three years does serious damage to
the herbaceous understory. In addition, the savanna will not carry a fire well
with all those woody shrubs hogging the savanna floor.

We have been burning our
savannas annually for 15 years (since 2002).

The best time to search for
undesirable woody plants is after a burn. This photo, of the Unit 10 savanna,
was taken on March 28, 2017 (the spring burn had been done on Feb 22, 2017).
Note the absence of woody vegetation (except for the blow-downs). You could
walk from one end of this savanna to the other without encountering a single
obstacle. Compare with the 2008 photo shown above.